Washington Revised Code Title 49. Labor Regulations § 49.48.170. Sales representatives--Payment

A principal shall pay wages and commissions at the usual place of payment unless the sales representative requests that the wages and commissions be sent through registered mail. If, in accordance with a request by the sales representative, the sales representative's wages and commissions are sent through the mail, the wages and commissions are deemed to have been paid as of the date of their registered postmark.